Influence of Cd, Sn and Ge on the pre-precipitation phase of the Al-Zn-Mg-Cd(Sn) and Cu-Be-Cd(Ge) solid solutions

The influence of Cd, Sn and Ge on the kinetics of the Guinier-Preston (GP) zones formation has been studied for the Al-7 %Zn-3 % Mg-0,05 % Cd(0,05 %Sn) and Cu-2 % Be-0,3 %Cd(0,3 % Ge) solid solutions. The volumic fraction of the formed GP zones is determined by a method based on microhardness measurements. Traces addition of Cd and Sn cause, respectively, a delay in the GP zones formation and an elimination of these zones, in Al-Zn-Mg-Cd(Sn). For the Cu-Be-Cd(Ge) alloys, the added Cd atoms accelerate the GP zones formation, while Ge atoms at a concentration of 0.3 % have no influence.